Tanner-Whitehouse bone age reference values for North American children

On the basis of 1090 x-ray films from 225 boys and 225 girls ages 8 to 16 years-participants in the Project Heartbeat longitudinal study who were living in a generally above-average income environment near Houston, Tex.-we provide Tanner-Whitehouse Mark 2 RUS (radius, ulna, and selected metacarpals and phalanges) bone age reference values for North American children of European origin. We designate these values as US90 (for the 1990s) reference values, in contrast to the original British bone age standards, called UK60 (for the 1960s). The US90 children matured considerably earlier than those on which the UK60 standards were based, though only about 3 months earlier than contemporary Spanish children. A study of 190 x-ray films from a research longitudinal series of 23 healthy boys in Virginia yielded values very close to the Houston values, confirming that our US90 reference values should be used in North America, pending a more extensive survey.